Tag: mesolithic

Transition to agriculture triggered demographic growth followed by collapse

Researchers have used two sets of data from the period 6000 to 2000 BC to investigate the demographics of the transition to agriculture in Europe: data from cemeteries, and radiocarbon dates from 24 well-documented archaeological regions across Europe.

The juvenility index is the proportion of a population aged between 5 and 19 years old: in an increasing population, this is high; in a declining population it is low. Researchers obtained data from 212 cemeteries, weighting results by settlement size. They then considered the Summed Calibrated Radiocarbon Date Probability Distribution (SCDPD) of 8,032 radiocarbon dates, which can be used as a proxy for population density and indicate whether populations are rising or falling at a given time.

Both sets of data gave similar results. The transition from Mesolithic to Neolithic in each region was accompanied by a sharp increase in the population, but after a period of stability there was a decline. The cemetery data indicated a period of growth lasting for about 720 years, a period of stability lasting for just under 1,000 years, followed by a decline. The use of radiocarbon dates is less proven as a proxy, but because far more data is available it should provide higher resolution results. The radiocarbon dates indicated that the period of growth had lasted for 420 years before a decline set in, lasting for 840 years for a complete boom to bust cycle of 1,260 years. That the two sets of results are reasonably consistent confirms SCDPD as a valid demographic proxy.

A newly-published genetic study of ancient DNA obtained from prehistoric human remains in Sweden has provided a fresh insight into the transition to agriculture in Scandinavia.

The ability to obtain DNA from the remains of prehistoric people has in recent years added a new dimension to the long-running quest to understand the demographics of the transition from hunter-gathering to farming in Neolithic Europe. Studies based on living populations have been unable to provide definitive answers, as ancient genetic signals are often blurred by far more recent events.

Researchers at Stockholm University and Uppsala University obtained genetic material from the remains of six hunter-gatherers and four farmers from the Scandinavian Neolithic, dating to around 5,000 years ago, together with a late Mesolithic hunter-gatherer from 7,500 years ago. The samples were obtained from mainland Sweden and the Swedish island of Gotland.

It was found that the genetic diversity of the hunter-gatherers was far lower than that of the farmers and of any present-day Eurasian populations, suggesting that their population sizes were very small. Fluctuating climatic conditions and/or restricted carrying capacities might have affected hunter-gatherer population sizes. It is also possible that the genetic diversity of the hunter-gatherers never recovered from population crashes occurring during the Last Glacial Maximum when European populations were confined to a few ice-free refugia.

A significant finding was that the hunter-gatherer and farming populations were genetically distinct from one another, confirming the view that agriculture was spread across Europe by migrating farmers, rather than by indigenous hunter-gatherers simply taking up farming. In other words, it was farmers and not just farming that spread.

The researchers also found evidence for genetic admixing between the hunter-gathering and farming communities – but it was one way. Hunter-gatherers apparently married into the farming communities, but not the other way round. Thus the expanding farming communities assimilated indigenous hunter-gatherers.

The study, published in the journal Science, is part of a recently-launched initiative to investigate ancient human remains in Scandinavia. Known as the Atlas project, it is being conducted by researchers at Stockholm University and Uppsala University.

Agriculture reached Britain and Ireland around 4000 BC, but the means by which the transition from hunting, fishing and gathering occurred has been debated for many years. One view is that indigenous Mesolithic people acquired domesticated crops and animals from continental Europe, but retained much of their existing lifestyle. Another is that Neolithic farmers arrived from the continent and spread rapidly. This latter scenario proposes that a rapid acculturation of indigenous Mesolithic people followed.

Previous work has considered stable carbon isotope signatures of bone collagen extracted from Mesolithic and Neolithic human remains. The results suggested that in coastal environments, the Mesolithic diet included a significant amount of marine protein, but that of the Neolithic farmers was predominantly terrestrial-based. However, doubts have been expressed about the sensitivity of the bone collagen stable isotope analysis to low-protein diets; quantities of less than 20 percent marine protein in the diet would be undetectable. Possible Neolithic shell middens from Scotland and Ireland suggest that seafood continued to be eaten.

To address this uncertainty, researchers analysed lipid residues recovered from Neolithic pottery sherds from coastal sites in Britain, the Scottish Isles, and Ireland. To extend the chronological period, material was also included from sites dating to the Bronze Age through to the Viking period. The results confirmed the near-complete absence of marine protein from the Neolithic diet and the strong presence of dairy products. This remained the case during the Bronze Age, and it was not until Viking times did marine protein again become a significant dietary item.

Similar studies in the Baltic region indicate a different pattern. There, hunting, gathering and fishing continued alongside farming. The contrasting patterns occurring at the same time in different regions suggest geographically-distinct ecological, demographic and cultural influences dictating the adoption of agriculture. The rapid shift to an intensive dairy economy is consistent with the low frequency of lactose intolerance among modern inhabitants of northwest European archipelagos. The evolutionary processes driving lactase persistence in adults would have been driven by the increasing importance of dairy products in the diet.

Reference:
Cramp, L. et al., Immediate replacement of fishing with dairying by the earliest farmers of the northeast Atlantic archipelagos. Proceedings of the Royal Society B281 (2014).

Study finds evidence of strong positive selection for skin, eye and hair pigmentation over last 5,000 years.

Why do people living in the tropics have dark skin whereas those living in higher latitudes have lighter skin? The traditional explanation is that is an evolutionary balancing trick between protection from skin cancer on one hand and the synthesis of Vitamin D by skin cells on the other. Dark skin results from higher levels of the pigment melanin: for those living nearer the equator, higher melanin levels provides a better protection from the sun’s more intense UV radiation; conversely, for those living at latitudes where UV radiation is weaker, the protection is not required and high melanin levels would block the production of Vitamin D.

However, things may not be quite so straightforward. A study carried out in 2012 at the University of Porto in Portugal considered alleles (variants) of four genes known to be associated with pigmentation, using samples taken from present-day Portuguese and sub-Saharan Africans. The evolutionary history of the four genes was estimated using a statistical model (Monte Carlo) to simulate the effects of genetic drift, natural selection and mutation. It was found that three of the alleles linked to lighter pigmentation did not start to sweep through European populations until around 11,000 to 19,000 years ago – at least 40,000 years after modern humans left Africa (Beleza, et al., 2012).

Two recently-published studies have investigated ancient DNA extracted from prehistoric human remains in Europe. The first study, published in the journal Nature, considered the pigment genes of DNA obtained from human remains found at the Mesolithic cave site of La Braña-Arintero, near León, Spain. The remains were identified as those of a male hunter-gatherer, who lived 7,000 years ago. He was found to have been dark-skinned and blue-eyed. Although present-day Spaniards are darker-skinned than northern Europeans, they are far paler than Africans (Olalde, et al., 2014). The result again suggests that paler skin colour was a fairly late development.

The second study, published in the journal PNAS, considered the pigment genes TYR, HERC2 and SLC45A2. TYR produces the enzyme tyrosinase, which is used as a catalyst in the production of melanin. HERC2 is responsible for determining eye colour; and SLC45A2 is involved in the distribution and processing of tyrosinase and other pigment-producing enzymes. The various alleles of these genes are responsible for different colours of skin, hair and eyes. Researchers extracted ancient DNA from 63 Chalcolithic (6500 to 5000 years old) and Bronze Age (5000 to 4000 years old) individuals from Ukrainian sites on the Pontic-Caspian steppe. 43 individuals yielded DNA from which the pigment genes could be sequenced, and these were compared with those of present-day Ukrainians.

The researchers found that the pigmentation of the prehistoric population differed from that of the present-day Ukrainians. The latter have 8.5 times as many alleles of TYR related to light skin colour as did their prehistoric forbears. Alleles of HERC2 related to blue eye colour were also far more common in the present-day population. However, none of these lighter pigmentation alleles are present in African populations. Thus it seems that the shift to lighter pigmentation was underway in the Chalcolithic and Bronze Ages, but it was at that stage incomplete – despite the immense passage of time since modern humans had left Africa. Computer simulations showed that these effects could not be explained by genetic drift alone, and that natural selection must have been a factor (Wilde, et al., 2014).

The team speculated that selection for lighter skin colour was related to the change in diet following the arrival of agriculture. The diet of hunter-gatherers was more likely than that of the farmers to include items rich in Vitamin D, such as fish and liver. To make up the difference, individuals needed to be able to synthesise it more efficiently – hence a lighter skin colour. At the same time, the trend to lighter hair and eye colour may have been the result of sexual selection: the initially-unusual colouring might have been more attractive to the opposite sex (the researchers noted that this phenomenon has been documented in guppies).

Study indicates that foragers maintained way of life alongside farming communities.

Farming spread across Europe from Southwest Asia between 6500 and 4000 BC, but interactions between the indigenous Mesolithic hunter-gatherers and incoming Neolithic farmers are poorly understood. The general view is that hunter-gathering disappeared soon after the arrival of agriculture, but whether the hunter-gatherers took up farming themselves or simply died out remains uncertain.

In order to investigate relationships between foragers and farmers, researchers examined Mesolithic and Neolithic samples from Blätterhöhle, a cave site near Hagen in North Rhine-Westphalia, Germany (Bollongino, et al., 2013). The cave contained the remains of around 450 Neolithic and Mesolithic individuals. It is likely that it was a burial ground, and that these individuals were deposited there deliberately. Radiocarbon dating has revealed two phases of occupation: a Mesolithic occupation from 9210 to 8340 BC, and a Late Neolithic occupation from 3986 to 2918 BC.

Stable isotope analysis and ancient mitochondrial DNA extraction was carried out on the bones and teeth of 29 individuals. Isotopic ratios of sulphur, nitrogen and carbon in human remains can provide an insight into the diet of an individual while they were alive. Mitochondrial DNA can trace maternal ancestry.

Of the 29 individuals sampled, 25 yielded usable mitochondrial DNA; five from the Mesolithic occupation and 20 from the Late Neolithic occupation. The five Mesolithic-era individuals all belonged to mitochondrial haplogroup U, in common with other pre-Neolithic hunter-gatherers of central, eastern and northern Europe. More unexpectedly, twelve of the Neolithic-era individuals also belonged to haplogroup U. This haplogroup is rare among Late Neolithic farmers, and suggests a surprising persistence of Mesolithic maternal ancestry. The remaining eight individuals belonged to typical Neolithic haplogroups.

Stable isotope analysis indicated the existence of three distinct groups. The first, comprising the Mesolithic-era individuals, subsisted on a diet of wild foods typical of that found at other inland Mesolithic sites. The second group comprised Late Neolithic individuals with a diet of domesticated animals typical of German Neolithic sites. The third group was also from the Late Neolithic, but diet was unusual: low in plant and animal protein and high in freshwater fish.

The members of this third group all belonged to mitochondrial haplogroup U, whereas members of the contemporary second group were a mixture of Mesolithic and Neolithic haplogroups. Thus it appears that a group of fisher-foragers were living alongside a group of farmers in the fourth millennium BC, which is around 2,000 years after agriculture reached central Europe. That both groups used the Blätterhöhle cave site at the same time indicates that they were near-neighbours.

Ethnographic data shows that such communities do live side by side, commonly exchanging food; for example cereals for fish. While forager women do marry into farming communities, the reverse is very rare as women from farming communities regard it as marrying down. The mitochondrial results are consistent with the ethnographic picture: no Neolithic haplogroups were found among the fisher-foragers; but the Mesolithic haplogroup U was present among the farmers.

It is unclear just how prevalent such forager communities were in Late Neolithic Europe, but the Blätterhöhle results are the strongest indication yet that such genetically-distinct communities persisted long after the arrival of farming. The ultimate fate of these communities remains uncertain. The authors of the study suggest that some groups may have eventually changed over to farming, although it has been suggested that incoming farmers would rapidly appropriate all the prime farmland, making such a switch problematic (Bellwood, 2005).

The Iron Gates are a series of gorges situated on the Danube between the Carpathian Mountains and the Dinaric Alps. In the early millennia after the last Ice Age, the region supported a number of sedentary or near-sedentary Mesolithic communities. At the sites of Lepenski Vir, Padina and Vlasac, fishers exploited migratory sturgeon, catfish, carp and other species (Borić, 2002).

There is no evidence for long-distance interactions during the early Mesolithic period from 9500 to 7400 BC, but these increased during the period from 7400 to 6200 BC. Archaeological evidence is based on the presence of the marine gastropods Columbella rustica and Cyclope neritea, which must have come from coastal regions more than 400 km (250 miles) away. This period was characterised by long-lasting and evidently successful communities. A large number of burials have been excavated, with bodies typically in the extended supine position characteristic of Mesolithic inhumations (Borić & Price, 2013).

The period between 6200 and 6000 BC saw a Mesolithic to Neolithic transition in the region, and was characterised by cultural hybridity (Borić & Price, 2013). At Lepenski Vir, remarkable trapezoidal, semi-subterranean, flat-roofed dwellings were constructed on the banks of the Danube (Borić, 2002). They varied in size from 5 to 30 sq. m. (54 to 320 sq. ft.), with the wider ends facing the river. The floors were dug 0.5 to 1.5 m (1 ft. 8 in. to 3 ft. 3 in.) into the terraced slopes of the river bank, and were surfaced with reddish limestone plaster. Inside, elongated pits lined with limestone blocks served as hearths (Mithen, 1994; Borić, 2002). Many houses contained burials, although burials were also placed outside houses (Radovanovic, 2000). Human/fish anthropomorphic sculptures carved from boulders were also found in many of the houses. These have been interpreted as evidence of a belief system characterised by a totemic relationship between humans and the fish that were so vital to their subsistence economy (Borić, 2005). In addition to these indigenous elements, Neolithic elements including pottery and polished stone axes appeared at Lepenski Vir (Borić & Price, 2013).

At this stage, the lack of domesticated animals at suggests that subsistence patterns remained unchanged. Mortuary practices were still characterised by typical Mesolithic extended supine burials during this period. However, the Early Neolithic site of Ajmana, in the downstream area of the gorges, was contemporary with these indigenous forager communities. By 6000 BC, further changes were evident in the region with the first appearance of crouched/flexed burials characteristic of the Neolithic period. The trapezoidal buildings of Lepenski Vir were replaced by more typical Neolithic constructions, and there was an increase in the number of settlements across the region as a whole (Borić & Price, 2013).

In total, over 500 graves have been excavated from the Mesolithic and Early Neolithic periods in the Danubian Iron Gates, and stable isotope analysis of the remains has provided considerable insight into the transition to agriculture in the region. Dietary data inferred from carbon and nitrogen isotope analysis of bone collagen suggests that after around 6200 BC, there was a shift from the Mesolithic reliance on the locally-abundant fish to a cereal-based diet. Strontium isotope data from dental enamel indicate that at the same time, burials of non-local first-generation migrants increased significantly. These burials are predominantly of the crouched/flexed type. Notably, 87Sr/86Sr ratios of these migrants fall both above and below local values, suggesting that they originated from at least two geologically-distinct regions. The dating of remains suggests that they might have arrived in several waves (Borić & Price, 2013).

Paradoxically, it appears that during the earliest stages of the Neolithic in southeastern Europe, Neolithic farmers were more mobile than the indigenous foragers, who remained tied to their Danubian fishing niche. The data from Lepenski Vir shows that during the transitional period, more nonlocal women than men were buried at the site. The suggestion is that women came to the site from Neolithic communities as part of an ongoing social exchange. At the same time, the numbers of Neolithic-type artefacts at the site testify to an increasing Neolithic presence in the region, and the Mesolithic way of life came under growing pressure. The period of co-existence lasted for two centuries between 6200 and 6000 BC, but in the centuries thereafter the foragers were completely absorbed into the farming communities and their way of life finally vanished (Borić & Price, 2013).

The familiar terms “Stone Age”, “Bronze Age” and “Iron Age” are part of the so-called Three Age system, introduced by the Danish archaeologist Christian Jurgensen Thomsen in 1819 when he was curator of the collection of antiquities that subsequently became the National Museum of Denmark in Copenhagen. Thomsen was looking for a simple and logical system by which to arrange the collection which in common with those of other museums was in a chaotic state, overrun with prehistoric artefacts from all over the world. Thomsen was not the first to think of applying tool-making materials as a basis for classifying prehistoric cultures, although he was the first to actually do so. Thomsen lacked any means of dating his artefacts, but correctly guessed that stone had preceded bronze, which in turn had preceded iron. At the time – forty years before Darwin’s Origin of the Species – few suspected the true antiquity of mankind, with many still believing that the Earth was just 6,000 years old. Although the Scottish geologist Charles Hutton and others had begun to call this figure into question, in the early 19th Century it was still widely accepted.

As far back as 1860s, Thomsen’s original scheme was beginning to look lopsided and in 1865 the archaeologist Sir John Lubbock, a friend of Charles Darwin, published Pre-historic Times, which was probably the most influential archaeological textbook of the 19th Century. In it he introduced the terms “Palaeolithic” (Old Stone Age) and “Neolithic” (New Stone Age). We now know that the Palaeolithic encompasses all but a tiny fraction of human prehistory, beginning approximately 2.5 million years ago with the emergence of the first members of Genus Homo – i.e. the first human beings. Accordingly the Palaeolithic is in turn divided into Lower, Middle and Upper. The Lower/Middle transition is taken to be the point at which Mode 3 industries enter the archaeological record such as the predominantly Neanderthal Mousterian culture, at very roughly 300,000 years ago. The Middle/Upper transition, approximately 40,000 years ago, is the point at which unequivocal evidence for modern human behaviour is found.

In Africa the terms Early, Middle and Late Stone Age, or ESA, MSA and LSA respectively, are preferred, but the LSA also encompasses the Neolithic and Bronze Age as neither metallurgy nor agriculture reached sub-Saharan Africa until Iron Age times. To avoid confusion, I shall use only the term “Palaeolithic”, with its sub-divisions occurring at different times in different parts of the world. Such a scheme is generally used for later prehistory and I see no reason not to use it here also.

The division between the Palaeolithic and the Neolithic is now taken to be the Pleistocene/Holocene boundary, that is to say the end of the last ice age, at around 11,550 years ago. This is somewhat illogical division, equating a purely geological change to a system based on technology. Agriculture was independently adopted in several parts of the world and spread outwards from these nuclear zones, taking many millennia to reach some places, and necessitating the introduction of another division, the Mesolithic (Middle Stone Age) for regions where hunter gathering persisted. Conversely in parts of the world where proto-agriculture was practiced in late Pleistocene times, such as the Levant, the term Epipalaeolithic is used.

The transition from Neolithic to Bronze Age is equally ill-defined – there is generally a transitional period where stone and native copper tools are in mixed use; this transitional period is referred to variously as Chalcolithic, Eneolithic or simply Copper Age. This transition began at different times in different parts of the world, and was of different duration – the Copper Age began earlier in the Middle East, but in Europe the transition to the fully-fledged Bronze Age was more rapid.

The working of iron begins around 1200 BC in India, the Middle East and Greece, but again took time to spread to other parts of the world. The Iron Age continues on into historical times, not ending in Northern Europe until the Middle Ages.

This does to all intents and purposes give us a nine-age system:

Table 1.0: The career of Mankind (YA = Years Ago)

Archaeological/

Geological Time period

Events

Miocene (26m – 5m YA)

Proconsul (27m-17m YA)

Pliocene (5.0m – 1.64m YA)

Ardipithecus ramidus (5m – 4.2m YA)

Australopithecus anamensis (4.2m – 3.9m YA)

A. afarensis (4.0m 3.0m YA)

A. africanus (3.3m – 2.5m YA)

A. Garhi ()

Paranthropus aethiopicus (2.5m – 2.4m YA)

P. robustus (2.4m – 1.2m YA)

P. boisei (2.3m – 1.2m YA)

Lower Palaeolithic

(2.4m – 200,000 YA)

2.4m YA. Earliest true humans appear in Africa, though apparently sympatric with later “robust” australopithecines (Paranthropus). Now believed that early fossil hominids represent at least two synchronous (though not sympatric) human species, Homo habilis (brain size 590-690 cc) and Homo rudolfensis (750 cc). It is not known which if either was ancestral to later types.

800,000 YA. Homo Antecessor. Controversial taxon known only from Atapuerca in Northern Spain, believed by some to be the common ancestor of both modern man and the Neanderthals.

500,000 YA. Larger-brained (1,200 cc) and bigger-boned hominids are found in the fossil record in Africa, Asia and Europe. Traditionally referred to as “archaic Homo sapiens” but Homo heidelbergensis now favoured. Other types have been proposed such as Homo rhodesiensis and H. helmei. It’s all very confusing!

15-11,600 YA. Magdelanian culture in western Europe, final European Palaeolithic culture.

15,000-12,900 YA. Bølling-Allerød interstadial.

12,900 YA. Beginning of the Younger Dryas stadial.

12,000 YA. Jōmon culture in Japan, first use of pottery.

Epipalaeolithic (20,000 – 11,600 YA)

Ohalo II (20-19,000 YA)

Natufian culture (14,000-11,600 YA) in the Levant.

Holocene

Mesolithic (11,600 YA until adoption of agriculture)

11,600 YA. Last Ice Age ends.

11.6-6,000 YA. Hunter-gathering persists in many parts of the world.

Neolithic (11,600 – 6,500 YA and later in various parts of the world)

11,600 YA. Rapid transition to agriculture in Middle East and Anatolia.

Tools: Mode 5 (microliths).

9,200 YA Catalhoyuk – very large Neolithic settlement in Anatolia.

9,000 YA. Beginning of the “Wave of Advance” – expansion of proto Indo-European farmers from Anatolia.

9,500 YA. Çatal Höyük, Anatolia, apparently no more than a very large village.

8,500 YA. As sea levels rise, Britain becomes an island.

Chalcolithic (6,500 – 4,000 YA in various parts of the world)

Copper and stone tools in mixed use.

6,500 – 3,500 YA. The age of the great megaliths in Europe.

5,100 – 4,000 YA. Construction of Stonehenge.

Bronze Age (5,300 – 2,700 YA in various parts of the world)

4,500 YA. Construction of the pyramids in Egypt.

5,300-2,700 YA. Indus Valley civilization, India.

4,700-3,450 YA. Minoan civilization, Crete.

3,600-2,100 YA. Mycenaean civilization, Greece.

2,200 YA. Mediterranean Bronze Age collapse.

Iron Age (1800 BC into historical times)

1800 BC. First working of iron, in India.

800-450 BC. Hallstatt culture,

Central Europe.

450 BC. La Tene culture.

AD 43. Romans invade and conquer Britain.

Taxonomy

Within Class Mammalia (the mammals) humans are grouped with apes, monkeys and prosimians (lemurs, lorises, etc) within the order Primates. The term is due to Linnaeus, representing his view that humanity sat firmly at the top of creation’s tree (the self-styled Prince of Botany was also responsible for the term “mammal”, reflecting his now quite fashionable views about breast-feeding).

The majority of the 200 or so living species of primate are tropical or subtropical, living in rainforests. Most are arboreal (tree-dwelling) or at least spending much of their time in the trees. Even those that have forsaken this habit show arboreal adaptations in their ancestry. These include manipulative hands and often feet, with opposable thumbs and big toes; replacement of claws with nails; a reduced sense of smell and enhanced sight including colour and stereoscopic vision; locomotion based heavily on hind limbs and a common adoption of an upright posture; and finally a tendency for larger brains than comparably-sized mammals of other orders.

The anthropoids or simians (Suborder Anthropoidea) basically comprise the more human-like primates and include Old World monkeys, New World monkeys (including marmosets and tamarins), apes and finally humans. Other primates are traditionally lumped together as prosimians.

Historically, membership of Family Hominidae was restricted to humans and australopithecines, with the Great Apes being banished to a separate family, Pongidae. Both families were grouped with the gibbons, etc. in Superfamily Hominoidea (the Hominoids).

However this scheme is now known to be incorrect as chimps and gorillas are more closely related to humans than they are to orang-utans. Accordingly Pongidae is now “sunk” into Hominidae (it would also be incorrect to give the orang-utans their own family). The term “hominin” (from Tribe Hominini) is now gaining popularity, because it comprises humans and australopithecines, i.e. the “traditional” hominids. The term “hominine” (from Subfamily Homininae) is also sometimes encountered; this grouping adds gorillas and chimps, but not orang-utans. To get back to the original meaning of “hominid” and subtract the chimps we have to go down to the level of Subtribe Hominina. To my mind this is very confusing and pushing the envelope of what we can reasonably ask from Linnaean taxonomy, which is after all firmly rooted in Platonic Realism (Linnaeus was a creationist), rather than Darwinian principles. I see nothing wrong with the use of the term “hominid” so long as we are aware that it includes our cousins, the Great Apes.